I just beat the Elite Four yesterday. I went to Lumoise station, got the pass, and went to the city.
I entered the Battle Maison, battled like 14 times and the 3 girls never showed up. (The owners) I tried going through the door, and it didn't work. I tried triple battles too.
How do you battle the 3 girls?
Best Answer
The girls battle you at the 20th Match of your win streak in the different battle modes. After this you unlock the super mode, in which they will appear after a 50-win streak(source serebii)